I have a set of closed planar curves that I connected to “boundary surface” and despite the output displayed being “trimmed surfaces” no matter which display mode in the rhino viewport, there is no surface visible. Only when I bake the surfaces do they become visible as rhino objects.
I have no idea why it’s like that, but hoping you will.
Thanks in advance
Dag Arnoud-
Since you didn’t categorize your post, I’ll have to guess that this is a Grasshopper question.
Please post a minimal gh file with all relevant Rhino geometry internalized.
Also please run the Rhino SystemInfo command and copy-paste the result here.
-wim
Is the red icon selected to “Draw shaded preview geometry”?
Is the surface component visible? 
May try to recompute your grasshopper file. But to help you it would be necessary to post the gh-file.
Excuse me for not responding. I was very busy at the time and preparing to leave for a big trip. I don’t remember if I ended up solving it, but I forgot what it was related to. Either way, thanks for your help 